Output director vane for an aircraft turbine engine, with an improved lubricant cooling function using a heat conduction matrix housed in an inner duct of the vane

ABSTRACT

A guide vane for a dual flow aircraft turbine engine, the aerodynamic part of the vane including an inner duct for lubricant cooling extending in a main direction and being partly bounded by a pressure side wall and a suction side wall of the vane. A heat conduction matrix is lodged in the duct, and presents main heat transfer wings extending parallel to the direction, and laid out in staggered rows.

TECHNICAL FIELD

This invention relates to the aircraft dual flow turbine engines field, and in particular the design of guide vanes arranged in the entirety or part of an air flow from a turbine engine fan.

This pertains preferably to outlet guide vanes, also known as OGV, designed to straighten the airflow at the fan outlet. Alternatively or simultaneously, if necessary, guide vanes could be placed at the fan inlet. The guide vanes are classically arranged in the turbine engine secondary vein.

The invention preferably pertains to an aircraft turbojet equipped with such outlet guide vanes.

PRIOR STATE OF THE ART

On some dual-flow turbojets, there have been instances where the outlet guide vanes are implemented downstream of the fan to straighten the flow coming out of it, and also eventually to provide a structural function. This last function is indeed intended to allow the duct of efforts from the centre of the turbine engine to an outer ring located in the extension of the fan housing. In this case, a motor attachment is classically arranged on or near this outer ring, to ensure the attachment between the turbine engine and a hanging mast on the aircraft.

Recently, it has also proposed to allocate an additional function to the outlet guide vanes. It is a heat exchanger function between the outside air traversing the crown of the outlet guide vanes, and the lubricant circulating inside the vanes. For example, this heat exchanger function is known from document U.S. Pat. No. 8,616,834, or document EN 2 989 110.

The lubricant designed to be cooled by output guide vanes can come from different zones of the turbine engine. Indeed, a lubricant can be circulating through the lubrication enclosures for the antifriction bearings supporting the engine shafts and/or the fan hub, or even a lubricant dedicated to the lubrication of the mechanical transmission components of the AGB (“Accessory Geared Box”). Finally, it can also be used for lubrication of a gearbox to drive the fan, where such gearbox is expected on the turbine engine in order to decrease the fan rotation speed.

The growing lubricant needs require us to adapt accordingly the heat dissipation ability associated with heat exchangers used for lubricant cooling. The fact of attributing a heat exchanger role to the outlet guide vanes, as in the solutions mentioned in the two documents cited above, allows in particular to decrease, or even to remove conventional exchangers of type ACOC (Air Cooled Oil Cooler). These ACOC exchangers are generally arranged in the secondary vein, their reduction/suppression allows to limit the disruption of the secondary flow and thus increase the overall turbine engine performance.

However, the solutions proposed in the prior art remain perfectible. In particular, there is a need to improve the heat exchanges to further increase the heat dissipation capacity. There is a need for reinforcement of the mechanical strength when facing high pressures generated by the circulation of lubricant within these vanes. This need for reinforcement of the mechanical strength is also even more important in the particular case of a guide vane with a structural function.

DISCLOSURE OF THE INVENTION

To meet these needs at least partially, the purpose of the invention is first aimed at a guide vane to be arranged in all or part of an air flow from a dual flow aircraft turbine engine fan, the guide vane including a foot, a head, and an aerodynamic flow straightening part laid out between the vane foot and head, said aerodynamic vane part having a first inside lubricant cooling duct extending in a first main cooling lubricant flow direction from the vane foot to the head, said first inner duct being partly bounded by a pressure side wall and a vane suction side wall.

According to the invention, the vane has a first matrix of heat conduction lodged in said first inner duct and including rows of main heat transfer fins following one another in the first direction parallel to which extend such main fins, these being spaced from each other in the first direction as well as a transverse direction of the vane going from a leading edge to a trailing edge of its aerodynamic part, so that at least some of the said main fins are arranged substantially staggered. In addition, each row includes junction fins connecting each two main fins directly consecutive according to transversal management, said junction fins on the same row being alternately in inside contact with the pressure wall and the suction wall in order to form, with the main fins they connect, a transverse structure having a general cradle form, also named crenellated.

Thus, the orientation and arrangement of the fins provide a satisfactory mechanical strength and high heat performance, while limiting the load losses suffered by the lubricant traversing through the first inner duct equipped in the fins.

The invention also shows at least one of the following optional features, taken alone or in combination.

The director vane includes, at the level of the foot or the head of the vane, an opening for the introduction of the first heat conduction matrix in the first interior duct. The location of the opening introduction significantly reduces the risk of leakage and of accidental introduction of lubricant in the fan air flow. On the other hand, this design allows creating vane parts in a single pass that bound the first inner duct, to obtain a better mechanical strength.

The first heat conduction matrix includes at least one zone in which said heat transfer fins are planned in a density between 1 and 5 fins/cm².

Said first heat conduction matrix provides a variable density of fins, even if alternatively, a reasonably uniform density can be planned within this first matrix. This ability to vary the density of the fins in particular to locally adapt the heat exchange between the lubricant and the secondary flow. As an indication, the density can be reduced in zones where the heat exchange coefficient with the air is the greatest, while conversely, the fin density is preferentially increased in zones where the heat transfer coefficient is the lowest.

This ability to vary the fin density within the first inner duct, in a transverse direction to the vane, also allows to check the homogeneity/heterogeneity of lubricant flow in this same direction, depending on the needs encountered. This faculty is also preferably implemented in the second duct mentioned below.

The first heat conduction matrix may present at least a first zone and a second zone offset from the first zone in the transverse direction, the second zone with an average height between the pressure side and suction side that is lower than the average height of the first zone, and said first zone having an average fin density greater than that of the second zone. This special design allows advantageously to get a more or less homogeneous lubricant flow in the transverse direction of the first inner duct, despite its evolutionary height along this same direction. In the same spirit, it is possible to consider a variable fin pitch, so that you have an always equal hydraulic cross-section.

In addition, said first duct may define a lubricant thawing channel extending along the first main direction, said channel being devoid of fins all along it and along the first heat conduction matrix. Alternatively, it may be a channel in which the main wings of the first matrix are located, but in a lower density than that adopted in the adjacent areas. In both cases, this allows to manage the specific flight phases in which the lubricant drops to very low temperatures, giving it a high viscosity. Indeed, thanks to this so-called “thawing” channel planned within the first inner duct, the lubricant can flow easier through this duct through the dedicated channel, and allows at the same time to warm the frozen lubricant between the fins of the zones adjacent to said channel. In this respect, it is stated that thawing channel is preferentially planned at one of the ends of the first inner duct, depending on the transverse direction of the latter.

It should be noted that the vane might only include a single first duct, ensuring the flow of lubricant radially outward. In this case of figure, the crown of guide vanes would include at least one other vane of similar design, with an inner duct also equipped with a heat conduction matrix, ensuring the flow of lubricant radially inward. Nevertheless, the lubricant must not necessarily return radially towards the hub via another vane. It can for example be reintroduced radially inwards by other known elements from the turbine engine.

However, the aerodynamic vane part is preferably also a second inside lubricant cooling duct spreading in a second lubricant flow from the head to the foot of the vane, said second inner duct being partly bounded by the vane pressure side wall and suction side wall, a second heat conduction matrix being housed in said second inner duct and including rows of successive main heat transfer fins along the second direction at the same time that extend such main fins, these being spaced from each other in the second direction as well as the transverse direction to at least some of the said main fins are arranged substantially in staggered manner in the second inner duct. In addition, each row includes junction fins connecting each two main fins directly consecutive according to transversal management, said junction fins on the same row being alternately in inside contact with the pressure wall and the suction wall in order to form, with the main fins they connect, a transverse structure having a general cradle form.

One possibility, the first and second inner ducts each extend separately throughout the aerodynamic part of the vane.

According to another possibility, the fluids of the first and second inner ducts are connected to one another near the head of the vane, and the average density of fins within the first inner duct is preferably less than the density of fins within the second inner duct. Indeed, since the lubricant is colder in the return direction adopted within the second inner duct, it makes it possible to increase the heat power exchanged by increasing the average fin density in this second duct.

Preferably, the guide vane has a structural function, in the sense that it permits transmitting forces from the centre of the turbine engine to an outer ring located in the extension of the fan housing.

The invention is also intended for aircraft turbojets, preferably a turbojet including a plurality of guide vanes such as those described above, arranged downstream or upstream of a turbine engine fan.

Finally, the invention is a method for manufacturing such a guide vane, the said aerodynamic vane part being made from a single piece so as to reveal the first inner duct, and the first heat conduction matrix is inserted in the said first inner duct. The matrix can be produced in a conventional manner, or else using the additive manufacturing technique. It is noted that the additive manufacturing proves to be perfectly suited to the production of the heat conduction matrix, in particular because this technique makes it possible to easily vary the density of the main conduction heat fins.

Other advantages and features of the invention will appear in the open-ended detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be made in the light of the attached drawings including;

FIG. 1 showing a schematic view side of the turbofan according to the invention;

FIG. 2 represents a magnified, more detailed view of a turbofan outlet guide vane shown in the previous figure, according to a preferred first embodiment of the invention;

FIG. 3 is a magnified view of a part of the outlet guide vane shown in the previous figure;

FIG. 3a is a perspective view of a part of the guide vane shown in FIG. 3;

FIG. 3b is a sectional view taken along line IIIb-IIIb of FIG. 3 a;

FIG. 3c is a magnified view of a part of the guide vane shown in FIG. 3 a;

FIG. 4 corresponds to a sectional view taken along line IV-IV of FIG. 3;

FIG. 4a is a similar view of that in FIG. 4, with the vane positioned in accordance with an alternative embodiment;

FIG. 5 shows the operation of the heat exchanger formed by the outlet guide vane shown in the previous figures, according to a first principle of operation;

FIG. 6 is a view similar to that of FIG. 5, with an outlet guide vane in the form of a second preferred embodiment of the invention;

FIG. 7 is a view similar to that of FIG. 4, with an outlet guide vane in the form of a third preferred embodiment of the invention;

FIG. 8 is a view similar to that of FIG. 4, with an outlet guide vane in the form of a fourth preferred embodiment of the invention;

FIG. 9 is a view similar to that of FIG. 5, with an outlet guide vane in the form of a fifth preferred embodiment of the invention;

FIG. 10 corresponds to a sectional view taken along line X-X of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, it represents a dual-flow and a dual-body turbojet 1, with a high dilution rate. The turbojet 1 is classically comprised of a gas generator 2 on either sides of which are arranged a low pressure compressor 4 and one low pressure turbine 12, this gas generator 2 comprising a high pressure compressor 6, a combustion chamber 8 and a high pressure turbine 10. Subsequently, the terms “front” and “back” are considered in an opposite direction 14 to the main flow direction of the gases within the turbojet, this direction 14 being parallel to its longitudinal axis 3. However, the terms “upstream” and “downstream” are considered according to the main flow direction of the gas within the turbojet.

The low pressure compressor 4 and the low pressure turbine 12 form a low pressure body, and are connected to each other by a low-pressure shaft 11 centred on the axis 3. Similarly, the high pressure compressor 6 and the high-pressure turbine 10 form a high pressure body, and are connected to each other by a high pressure shaft 13 centred on the axis 3, and arranged around the low pressure shaft 11. The shafts are supported by antifriction bearings 19, which are lubricated by being arranged in oil enclosures. The same applies to the fan hub 17, also supported by the antifriction bearings 19.

The turbojet 1 is also comprised of, at the front of the gas generator 2 and the low pressure compressor 4, a single fan 15 which is arranged here directly in the back of an engine air intake cone. The fan 15 is rotating about the axis 3, and surrounded by a fan housing 9. In FIG. 1, it is not driven directly by the low pressure shaft 11, but only indirectly driven by the shaft via a gearbox 20, which allows it to turn at a slower speed. Nevertheless, a direct drive solution of the fan 15, by the low pressure shaft 11, is part of the invention.

In addition, the turbojet 1 defines a primary vein 16 intended to be traversed by a primary flow, as well as a secondary vein 18 intended to be traversed by a secondary flow located radially outward from the primary flow, the fan flow thus being divided. As skilled industry persons know, the secondary vein 18 is bounded radially outward in part by an external ring 23, preferably metal, extending to the rear fan housing 9.

Although this has not been represented, the turbojet 1 is equipped with a set of equipment, for example of types fuel pump, hydraulic pump, alternator, starter, variable pitch stator actuator (VSV), discharge vane actuator, or even electric power generator. This includes equipment for lubrication of the gearbox 20. These equipment are driven by an accessory box or AGB (not shown), which is also lubricated.

Downstream from the fan 15, in the secondary vein 18, a crown of guide vanes is planned which here are outlet guide vanes 24 (OGV). These stator vanes 24 connect the external ring 23 to a housing 26 surrounding the low pressure compressor 4. They are spaced from each other on the circumference, and allow to straighten the secondary flow after it passes through the fan 15. In addition, these vanes 24 may also have a structural function, as is the case in some examples which are described herein. They ensure the transfer of the forces from the gearbox and the antifriction bearings 19 on the engine shafts and the fan hub, towards the outer ring 23. Then, these forces may transit through an engine attachment 30 attached on the ring 23 and linking the turbojet to a hanging mast (not shown) of the aircraft.

Finally, the outlet guide vanes 24 ensure, in the examples that are currently described, a third heat exchanger function between the secondary airflow traversing the crown of vanes, and the lubricant circulating inside the vanes 24. The lubricant designed to be cooled by the outlet guide vanes 24 is the one used for the lubrication of antifriction bearings 19, and/or the turbojet equipment, and/or accessories box, and/or the gearbox 20. These vanes 24 are thus part of the fluid circuit(s) in which the lubricant is put into circulation to successively lubricate the associated elements, then to be cooled.

In reference to FIGS. 2 to 5 now, we will describe one of outlet guide vanes 24, according to a first preferred embodiment of the invention. In this respect, it is noted that the invention as it will be described with reference to FIGS. 2 to 5 may apply to all vanes 24 in the stator crown centred on the 3 axis, or only some of these vanes.

The vane 24 can be strictly of radial orientation as shown in FIG. 1, or be slightly tilted axially as shown in FIG. 2. In all cases, it is preferentially straight in the side view such as shown on FIG. 2, while extending in a longest extent direction 25.

The outlet guide vane 24 is comprised of an aerodynamic part 32 which corresponds to its central part, i.e. the one exposed to the secondary flow. On either side of this aerodynamic part 32 used to straighten the flow out of the fan, the vane 24 is respectively comprised of a foot 34 and a head 36.

The foot 34 serves for the attachment of the vane 24 on the low pressure compressor housing, while the head is used to attaching the same vane on the outer ring extending the fan housing. In addition, the vane 24 comprises at the foot and head levels, platforms 40 used to reconstruct the secondary vein between the vanes 24, in the circumferential direction.

The aerodynamic part 32 of vane, without its heat conduction matrices which will be described below, is from a single source, for example by so-called additive manufacturing using 3D printing or direct manufacturing. For example, additive manufacturing of the aerodynamic part 32 is carried out by one any of the following techniques:

-   -   Selective Laser Melting (SLM) or Electron Beam Melting (EBM);     -   Selective Laser Sintering (SLS) or by electron beam;     -   Any other type of powder solidification technique under the         action of an energy source of medium to high power, the         principle is to melt or sinter a bed of metal powder by laser         beam or electron beam.

The powder used is aluminium or titanium-based, or based on another metal material or any other material with good heat conduction characteristics.

The aerodynamic part 32 of the vane could, however, be made using more conventional techniques, allowing a hollowed out portion to appear in which the matrix would then be introduced, before placing a closing plate for example by welding, gluing or soldering.

Moreover, the manufacturing of a single part may also include the foot 34 and/or head 36 and/or platforms 40, without getting out of the scope of the invention.

In this first preferred embodiment of the invention, the aerodynamic part 32 is equipped with two inner ducts 50 a, 50 b substantially parallel one to the other, and parallel to the longest extent direction 25. More specifically, this is a first lubricant cooling inner duct 50 a, which extends in a first main direction 52 a of the lubricant flow. This direction 52 a is substantially parallel to the longest extent direction 25, and presents a direction going from the foot 34 to the head 36. Similarly, a second lubricant cooling inner duct 50 b is planned, which extends in a second main direction 52 b of lubricant flow within this duct. This direction 52 b is substantially parallel to the longest extent direction 25, and presents a reverse direction going from the head 36 to the foot 34. So, the first duct 50 a is planned to be traversed radially outward by the lubricant, while the second duct 50 b is expected to be traversed radially inward. To address the transition from one to the other, near the head 36, the radial external ends of the fluids of the two ducts 50 a, 50 b are connected by an elbow 54 to 180°, corresponding to a low made in the aerodynamic part 32.

Alternatively and in an equivalent manner for a vane of similar design, the first inner duct extends along its first main direction of flow of the lubricant which has a direction from the head to the foot, even though the vane could comprise only a single first duct. Similarly, in the case of the vane provided with the second inside lubricant cooling duct, this duct may extend along its second main direction having a direction going from the foot to the head.

The radial internal ends of the two ducts 50 a, 50 b are related to the lubricant circuit, sketched by the element 56 in FIG. 2. This circuit 56 includes in particular a pump (not shown), which can apply a desired flow direction to the lubricant within ducts 50 a, 50 b, namely the introduction of the lubricant by the inside radial end of the first duct 50 s, and the extraction of the lubricant at the inside radial end of the second duct 50 b. Couplings 66 ensure fluid communication between the inside radial ends of the ducts 50 a, 50 b and circuit 56, these fittings 66 traversing the foot 34.

The two ducts 50 a, 50 b as well as the elbow 54 form together a general U form, with the first duct 50 a and the second duct 50 b separated from one another in a transverse direction 60 of the vane substantially orthogonal to the longest extent direction 25. In this first preferred embodiment as well as in all other modes, to optimize the heat exchanges, the first duct 50 a is located on the trailing edge 62 side of the vane 24, while the second duct 50 b is located on the leading edge 64 side. However, a reverse situation can be retained, without getting out of the scope of the invention.

The aerodynamic part 32 of the outlet guide vane 24 has a pressure side wall 70, a suction side wall 72, a full zone 74 connecting the two walls 70, 72 near the trailing edge 62, a full zone 76 connecting the two walls 70, 72 near the leading edge 64, as well as a central full zone 78. This last zone 78 connects the two walls 70, 72 to the level of a substantially central portion of these, depending on the direction of the vane cord It also serves as a structural reinforcement and extends from the foot 34 to the elbow 54, while the full zones 74, 76 extend substantially on the entire length of the part 32, in the longest extent direction 25. The first duct 50 a is formed between the walls 70, 72 and between the full zones 74, 78, while the second duct 50 b is formed between the walls 70, 72 and the full zones 76, 78. The pressure and suction side walls 70, 72 present substantially constant thickness, next to ducts 50 a, 50 b that they bound. However, 50 a, 50 b ducts extend transversely in the direction 60 having a variable height between the two walls 70, 72, as this can be seen in FIG. 4. Alternatively, these ducts could have a constant height, as shown schematically in FIG. 4a for the first duct 50 a. In the latter case, the two walls 70, 72 then adopt a variable thickness to obtain the aerodynamic profile of the vane.

The two lubricant cooling inner ducts 50 a, 50 b have the particular feature of integrating heat conduction matrices, provided in particular with main heat transfer fins. These matrices are also called convection matrices.

In the first preferred embodiment of the invention, the arrangement and shape of the main fins 80 are substantially identical in the two matrices 50 a′, 50 b′ respectively housed in the two ducts 50 a, 50 b. The main fins 80 are also planned to have the same densities, although this may be otherwise, as this will come out of the other embodiments which will be described later.

The two matrices 50 a′, 50 b′ being substantially identical, only the first matrix 50 a′ will be described, but it must be understood that this description is also applicable by analogy to the second matrix 50 b′ housed in the second inner duct 50 b.

As is visible in FIGS. 3-4, the first heat conduction matrix 50 a′ includes rows 81 of main heat transfer fins 80, these rows following each other in accordance with the first direction 52 a.

The main fins 80 are locally arranged substantially orthogonally to the pressure side and suction side walls 70, 72. In addition, they each extend in parallel to the first direction 52 a, these fins being spaced from each other in this same first direction 52 a, as well as depending on the transverse direction 60. They have an average height Hm, between the two walls, 70, 72, of the order of 4 to 8 mm. Their thickness E, depending on the transverse direction 60, presents a preferably constant value between 0.5 and 1.5 mm, preferably while their length L in the direction 52 a presents a preferably constant value between 1 and 4 mm. Moreover, the spreads/steps “P” between the fins 80 according to each of the two directions 52, 60, are for example of the order of 2 to 4 mm.

In at least one zone of the duct 50 a′, and preferably in the entirety of the latter, the fins 80 are arranged staggered, with a density for example of about 3 fins/cm². For example, more generally, the average density is included between about 1 and 5 fins/cm².

The special staggered arrangement of the fins 80, combined with their arranged length L in the main direction of flow 52 a, allows obtaining high heat performance by limiting the load losses suffered by the lubricant in operation.

In addition, each row 79 includes junction fins 80′ connecting every two main fins directly 80 directly consecutive under the transverse direction 60. The junction fins 80′ are arranged substantially orthogonally to the main fins 80, being located flat on the pressure side wall 70 or suction side wall 72. Specifically, the fins on the same row 79 are alternately in inside contact with the pressure side wall 70, and in inside contact with the suction side wall 72. Each row forms, with all of its main fins 80 and its junction fins 80′, a transverse structure with a general cradle form. As shown in FIG. 3a , the general cradle shaped rows 79 are offset transversely one from the other with a length corresponding to half a step “P”. The junction fins 80′ are of shape and size substantially identical to those of the main fins 80. In particular, they have the same length “L” and the same thickness “E”.

As this has been shown in FIG. 3c , junction fins 80′ are attached to the ends of the main fins 80 that they connect. Moreover, the junction fins 80′ located on the pressure side are connected to each other at the level of their edges, as well as the junction fins 80′ located on the suction side are connected to each other, also at the level of their edges. This allows the embodiment of all of the heat conduction matrix 50′ by additive manufacturing, for example in any one of the techniques previously exposed.

Once completed, each matrix 50 a′, 50 b′ is inserted in its associated duct 50 a, 50 b, from the foot 34 of the vane manufactured in one piece. The insertion is performed via an introduction opening 49 a, 49 b made through said vane foot 34, and presenting a section substantially identical to ducts 50 a, 50 b. These introduction ports 49 a, 49 b, shown in FIG. 2, then come out in the connections 66 leading to the circuit 56. A solution with plugs might also be used to partially plug the introduction ports 49 a, 49 b, after insertion of the matrices in the ducts. In this case, the weaker section connections 66 would connect to the plugs, at the level of a lubricant flow channel made through each of these plugs.

Each heat conduction matrix 50 a′, 50 b′ extends through all or part of the radial length of its associated duct 50 a, 50 b. Preferably, more than 80% of the radial length of each duct 50 a, 50 b is occupied by its corresponding matrix 50 a′, 50 b′.

During this operation of the turbine engine, the lubricant 82 drawn in FIG. 5 is introduced in the first inner duct 50 a, in the first direction 52 a heading radially outward. At this stage, the lubricant 82 presents a high temperature. A heat exchange is performed between this lubricant 82 conforming to the shape of the first heat conduction matrix fins (not shown in FIG. 5), and the secondary flow 81 conforming to the shape of the outer surface of the pressure side walls and suction side walls 70, 72 supporting these fins. The lubricant 82, after been redirected by the elbow 54 in the second duct 50 b, suffers in the latter a similar cooling, also by heat exchange with the secondary air flow 81 and circulating in the second main direction 52 b of flow. Then the cooled lubricant 82 is extracted from vane 24, and redirected by the closed-circuit 56 towards the elements to lubricate.

Referring now to FIG. 6, a second preferred embodiment in which ducts 50 a, 50 b are not connected within the aerodynamic part 32 of vane 24. They indeed stretch each separately on the length of the aerodynamic part 32, to connect the fluids to outside the vane 24. For example, to do this, a connection elbow 56 is planned arranged radially inward from the head of the vane 36, for example in support on this head.

Now, with reference to FIG. 7 representing a third preferred embodiment of the invention, it is expected that the density of the heat transfer fins 80 in the first and/or the second matrix 50 a′, 50 b′ is variable, that is non-uniform. Indeed, in this third mode, we seek a significantly homogeneous lubricant flow obtaining the transverse direction 60 of the first duct 50 a, despite its evolving height between the two pressure side and suction side walls 70, 72. Thus, for the first matrix 50′, a first zone Z1 is planned for example located upstream in the transverse direction 60 and thus far from the trailing edge 62, as well as an adjacent second zone Z2 located further downstream in the transverse direction 60, and thus closer to the trailing edge 62. The spacing between the pressure side and suction side walls 70, 72 is growing from the downstream end of the duct 50 a. Therefore, the second Z2 shows fins whose average height Hm2 is less than the average height Hm1 of fins 80 of the first zone Z1. Also, to get the substantially same uniformity of the lubricant flow in the transverse direction 60 of the duct 50 a, it is preferentially planned that the first zone Z1 has an average density of fins 80 higher than the density expected within the second zone Z2. This higher density in the zone Z1 is essentially achieved by bringing the fins 80 closer to each other, in the transverse direction 60.

Although it was not represented, a symmetrical layout can be adopted in the second duct, the spacing between the pressure side and suction side walls 70, 72 narrows towards the leading edge.

FIG. 8 represents a fourth preferred embodiment of the invention, in which the average density of fins 80 within the first matrix 50 a′ is less than the density of fins in the second matrix 50 b′. This allows increasing the heat power exchanged at the level of lubricant in the return direction, at a stage where it is colder because of the heat power has already been exchanged within the first ducts 50 a, in the lubricant outbound direction.

Finally, FIGS. 9 and 10 represent a fifth preferred embodiment, in which it is expected a thawing channel 90 a, 90 b, in each of the two inner ducts 50 a, 50 b. In the first duct 50 a, the channel 90 a runs parallel to the first direction 52 a, by being located closer to the trailing edge 62. Symmetrically, channel 90 b runs parallel to the second direction 52 b by being located closer to the leading edge 64. Here the position near the trailing edge was privileged, because this is the zone in which the heat exchange with the secondary air flow is the highest.

Each of these two channels 90 a, 90 b spans the entire length of its associated duct, coming out in the elbow 54. In this fifth preferred embodiment, each thawing channel 90 a, 90 b is deprived if fins 80 on its entire length, that is completely empty to promote circulation of cold lubricant by limiting load losses. Each channel 90 a, 90 b is thus bounded between the surface bounding the inner duct 50 a, 50 b, and an edge of the associated matrix 50 a′, 50 b′.

The presence of these channels 90 a, 90 b allows managing the particular flight phases in which this lubricant shows low temperatures, which makes it viscous and giving it so-called “freezing” aspect. Through these channels 90 a, 90 b, viscous lubricant can more easily flow through the inner ducts 50 a, 50 b, using the channels 90 a, 90 b located at the ends. The lubricant circulation within these channels 90 a, 90 b allows gradually warming the frozen lubricant in the other parts of the matrices 50 a′, 50 b′, between the main fins 80.

For an optimal operation, the width Lc of each channel 90 a, 90 b, in the transverse direction 60, is greater than the average transverse step Pm between the main fins 80 of its associated duct 50 a, 50 b. The ratio between these two dimensions Lc, Pm is preferably greater than 1.5, and more preferably greater than 2.

Alternatively, the channels 90 a, 90 b could present some main heat transfer fins 80, by integrating these channels in the matrices. At the level of the channels, the density of the fins 80 would then be lower than the one adopted in other zones of the matrices. This reduced density within the integrated channels 90 a, 90 b would then be obtained mainly by increasing the average transverse step between the fins 80, within these thawing channels 90 a, 90 b.

Of course, various changes can be made by a skilled person to the invention that has just been described, only as open-ended examples. In particular, the technical characteristics specific to each of the five embodiments described above can be combined between them, without getting out of the scope of the invention. Finally, it is noted that in the non illustrated case of the inlet guide vanes to straighten the airflow upstream of the fan, these vanes are arranged in the entire air flow of the fan around an inlet cone of non-rotating air, the vane feet being then related to this fixed cone of intake air. 

The invention claimed is:
 1. A guide vane to be arranged in all or part of an air flow of an aircraft turbine engine fan with dual flow, the guide vane comprising: a foot, a head, an aerodynamic part for straightening the flow arranged between the foot and the head of the vane, said aerodynamic part of the vane comprising a first inner duct for lubricant cooling extending in a first main direction of lubricant flow from the foot to the head of the vane, said first inner duct being partly bounded by a pressure side wall and a suction side wall of the vane, a first heat conduction matrix housed in said first inner duct and including rows of main heat transfer fins succeeding each other in the first direction parallel to the direction that such main fins extend, these being spaced from each other in the first direction as well as in a transverse direction of the vane from a leading edge to a trailing edge of its aerodynamic part so that at least some of the said main fins are laid out significantly staggered, and wherein each row includes junction fins, each junction fin connecting two of said main fins directly in a consecutive manner in the transverse direction, said junction fins being alternatively in inner contact with the pressure side wall and the suction side wall in order to form, with the main fins that they connect, a transverse structure in a general cradle form.
 2. The guide vane according to claim 1, further comprising, at the level of the foot or the head of the vane, an opening for the introduction of the first heat conduction matrix in the first inner duct.
 3. The guide vane according to claim 1, wherein the first heat conduction matrix comprises at least one zone in which such main heat transfer fins are planned in a density between 1 and 5 fins/cm².
 4. The guide vane according to claim 1, wherein the first heat conduction matrix has main fins with a variable density.
 5. The guide vane according to claim 4, wherein said first inner duct has at least a first zone and second zone offset from the first zone in the transversal direction, the second with an average height between the pressure side and suction side walls, which is less than the average height of the first zone, and that said first zone presents an average fin density greater than that of the second zone.
 6. The guide vane according to claim 1, wherein said first duct defines a lubricant thawing channel extending in the first main direction, said channel being devoid of fins on its entire length and follows along the first heat conduction matrix.
 7. The guide vane according to claim 1, wherein the aerodynamic part of the vane also has a second inner duct for cooling lubricant, extending in a second main lubricant flow direction ranging from the head to the foot of the vane, said second inner duct being partly bounded by the vane pressure side wall and a suction side wall, a second heat conduction matrix being lodged in said second inner duct and comprising rows of main heat transfer fins succeeding each other in the second direction in parallel with said main fins, these being spaced from each other similar to the second direction as well as in the transverse direction so that at least some of the said main fins are arranged substantially staggered in the second inside duct, and that each row includes junction fins, each junction fin connecting two of said main fins directly in a consecutive manner in the transversal direction, said junction fins being alternately in contact with the pressure side wall and the suction side wall in order to form, with the main fins that they connect to, a structure in a general cradle form.
 8. The guide vane according to claim 7, wherein each of the first and second inner ducts extend separately throughout the entire aerodynamic part of the vane, or wherein the first and second inner ducts are connected to each other near the vane head, the average density of fins within the first inner duct is less than the density of fins within the second inner duct.
 9. The guide vane according to claim 1, further comprising a structural function of transmitting forces from a center of the turbine engine to an outer ring located in an extension of a fan housing.
 10. An aircraft turbojet comprising a plurality of guide vanes according to claim 1, arranged downstream or upstream of a fan of the turbine engine.
 11. A manufacturing method of a guide vane according to claim 1, wherein said aerodynamic part of the vane is made in one piece so as to reveal the first inner duct, then the first heat conduction matrix is inserted in said first inner duct. 